Bug: assignfoldercombobox-unguarded-archiverootpath-read

[drmoisan]

• Work Mode: full-bug

Summary

QfcItemController.AssignFolderComboBox reads _globals.Ol?.ArchiveRootPath at
QuickFiler/Controllers/QfcItemController.FolderHandling.cs:233 with no try, and the method is
reached from the UI dispatcher. The null-conditional operator guards a null Ol; it does not guard
an ArchiveRootPath getter that throws when no archive root is configured. Guarding
FolderPredictor alone therefore does not prevent the failure at this call site.

Environment

• OS/version: Windows 11 Pro 10.0.26200, .NET Framework 4.8 VSTO add-in hosted by Outlook
• Python version: not applicable; this is C# in QuickFiler
• Command/flags used: not a command-line defect; reached through the QuickFiler item pane
• Data source or fixture: a profile whose Archive Root is unset, which is the state reported in
  issue 797 (Archive Root -> Outlook and File System both showing "Please select an archive")

Steps to Reproduce

1. Open a profile whose Archive Root has never been set, so ArchiveRootPath has no configured value.
2. Open QuickFiler on a mail item so the folder combo box is populated.
3. Observe the folder-handling path reach AssignFolderComboBox with _folderHandler.FolderArray
   non-empty.

Expected Behavior

An unset archive root degrades the suggestion display - the predetermined folder is simply not
preselected - and QuickFiler continues to operate.

Actual Behavior

The read at QuickFiler/Controllers/QfcItemController.FolderHandling.cs:233 propagates the getter's
exception out of AssignFolderComboBox. Because line 188 of the same file invokes the method through
_itemViewer.UiDispatcher.InvokeAsync(AssignFolderComboBox), the exception surfaces on the UI
dispatcher rather than at a handled boundary.

AssignFolderComboBox begins at line 191 and contains no try block; the read sits six lines after
_itemViewer.SetFolderSuggestions(_folderHandler.FolderRowArray) consumes FolderRowArray.

Logs / Screenshots

• Attached minimal logs or screenshot
• Snippet: none captured; the finding is from static reading of the call path, not from a runtime
  trace. A runtime trace should be captured as part of the fix.

Impact / Severity

• Blocker
• High
• Medium
• Low

Medium: it is a user-visible failure on a supported configuration (archive root unset), and it is
the reason issue 812's AC1 outcome can be verified at unit level but not end to end in QuickFiler.

Source

From: docs/features/potential/2026-09-08-assignfoldercombobox-unguarded-archiverootpath-read.md

[drmoisan]

Delivered by PR #836, merged into main as 0f0fd83 via the review-residuals-2026-09-08 epic.